In the field of semiconductor device manufacturing, numerous efforts have been made to increase the density of semiconductor devices through their miniaturization. Recently, attention is being directed to a semiconductor device stacking technique called three-dimensional (3D) packaging as means for increasing the density per unit area of semiconductor devices.
Semiconductor devices stacked in the vertical direction may include electrodes that are arranged to penetrate through a substrate including a silicon layer, for example. In this way, the semiconductor devices may be electrically connected via the electrodes. To create such an electrode that penetrates through a substrate, a resist is applied on the substrate using a coater, the resist is exposed using an exposure apparatus, and a resist pattern is developed using a developing apparatus. The resist is then used as a mask to etch the substrate using a plasma etching apparatus to create a hole portion such as a through hole or a via hole. After creating the hole portion in the substrate, the resist remaining on the substrate is removed by asking.
When etching a substrate including a silicon layer, for example, a plasma may be generated from an etching gas including a fluorine-containing compound gas such as SF6 gas and the substrate may be etched using the generated plasma.
The hole portion as described above generally has to be etched to a depth of approximately 100 μm. However, when the etching gas is made up of a fluorine-containing compound gas such as SF6 gas alone, etching by the plasma generated from such an etching gas tends to be isotropic. In this case, side walls of the resist pattern may be susceptible to etching as well. As a result, the substrate may be undercut or etched laterally and a side wall of the hole portion may not be arranged to have a vertical configuration.
In this respect, a technique is known that involves performing a step of forming a protective film on an upper face and a side wall of a resist pattern before starting a plasma etching step for etching a silicon layer, the protective film being formed using plasma generated from an etching gas for prompting deposition materials to be deposited on the substrate surface (see e.g., Patent Document 1). In this way, the side wall of the resist pattern may be prevented from being etched and undercut may be prevented.